As a background of this technology, JP-A-2007-120711 has been disclosed. In the application, with respect to a range of frequency of a damping object, a plurality of frequencies are selected and then control systems per each selected frequency are designed in advance. In this state, a control system designed to have a frequency which is the closest frequency to the natural frequency of the damping object is selected among the designed control systems and then the selected control system is incorporated into a controller of an active damping device.